Description: Armcx1 is a mitochondria-localized protein. Here we can see Armcx1-GFP (in green) and mitochondria (in magenta). The cell is a mouse embryonic fibroblast. Armcx1-GFP was overexpressed using a lipofectamine transfection. 

Purpose: Mitochondria-localized proteins usually localize to the entire mitochondria. The only other mitochondria protein that localizes to a specific subsection of the mitochondria is DRP1, a protein that is involved in fission. Fission is the process of mitochondria division and can occur for mitochondria to remove debris or to create new mitochondria. DRP1 acts like molecular scissors to pinch the mitochondria during fission. It usually localizes to the middle or ends of mitochondria tubules as these are the location of fission events. When we looked at Armcx1 in MEF cells we were surprised to see it localizing in puncta along the mitochondria, indicating it may also play a role in fission.  

Description: Top is a wild-type control mouse embryo at embryonic day 13. Bottom is an Armcx1 fl/fl Isl1 Cre KO mouse embryo at embryonic day 13. Left eyes of both embryos have been stained with a DiL crystal to trace axons down the optic nerve. Blue dashed line represents the midline of the skull and the point where the optic chiasm forms.

Purpose: In wanting to study Armcx1's endogenous function we first looked at its role in retinal ganglion cell (RGC) development. The RGC neurons project their axons out of the back of the eye and toward the brain. At the embryonic time point e13, these axons should be reaching the midline of the skull and forming the optic chiasm. When we delete Armcx1, we can see that the RGCs do project their axons out of the back of the eye, but they do not reach the chiasm at the expected time point. Suggesting that Armcx1 may play a role in regulating RGC axonal growth during development.